Written By: Jack Hinde
Edited By: Jovan Popovic
For the 2020 season, the MLB announced that they have appended rules that were in place to control relief pitcher usage. Previously, a pitcher had to face just a single batter before they were allowed to be removed from the game. Starting this past year, that number moved to a minimum of three. While there were many rule changes in place for the shortened season, such as seven inning doubleheaders and the runner on second base in extra innings rule. Considering that this was finalized before anybody was even thinking about the season not being able to run as usual is a good indicator that the three batter rule–along with the expansion of rosters to 26 players announced at the same time–is here to stay in MLB baseball.
The reasoning behind the rule change was to continue to raise pace of play to lower the length of games in time, something that Commissioner Rob Manfred Jr. has made one of his priorities since his starting in the position. One group of baseball players appear to be especially targeted by this new rule, and those players are the specialist relief pitchers. While this rule directly affects all relief pitchers, it hits the hardest for those who were specialists. Baseball centers heavily around handedness, and there is evidence of a “platoon advantage.” Batters have the advantage when the pitcher is of a different handedness, and pitchers have the advantage when the batter is of the same handedness. Specialist relievers had the role of making sure batters of a certain handedness were put out. After that, they would hand the ball to the next pitcher when they no longer had the platoon advantage.
From Paul Moehringer’s Pyramid Rating System Database, from 2017 to 2019, 64.4% of all batters (including pitchers) hit from the right side, 28.1% from the left side and 7.5% switch hit as to always have the platoon advantage. For pitchers over the same period 73.8% threw right-handed and 26.1% were left-handed (0.01% or Pat Venditte was the lone switch pitcher from 2017-2019), also from the Pyramid Rating System Database. Being that many of the pitchers are right-handed, left-handed batters faced left-handed pitchers infrequently, and so in a crucial spot perhaps late in a game, teams found it advantageous to bring in a pitcher who specialized in getting left-handed batters out to maximize the platoon advantage and take advantage of the unfamiliarity. Since these pitchers had a limited role, they often were very good at their niche task but wouldn’t remain in the game if they didn’t have the platoon advantage. The same pattern existed for right-handed specialists.
Many teams assemble their batting order avoiding batters of the same handedness consecutively, so these specialists were often called to get just one or two outs per appearance. With the rule change calling for a minimum of three batters faced, how much would their performance in 2020 suffer now that they had to be left in to face batters at a platoon disadvantage?
Looking from the period of 2017 to 2019, there were 55 pitchers who fit the criteria of being a specialist pitcher. The criteria used was that their batters faced per game pitched was less than 3.51, and that they appeared in at least 5 games. Of those 55 pitchers, 15 also appeared in 2020, and 13 of them appeared in at least 5 games. Below is a list of those 13 pitchers, their handedness, their games pitched, and ERA in both seasons, per fangraphs.com.
What immediately sticks out from the table is that just two of the pitchers are right handed, and we can see that comparing their performances in 2020 compared to 2017-2019. Chaz Roe posted a better ERA in 2020 than over the previous three seasons, whereas Sam Coonrod’s ERA jumped more than any other pitcher identified in the sample post-rule change, so there are not enough pitchers of both handedness to consider if the rule change helped one side more than the other.
The next question that needs to be asked is whether these pitchers all fit the same role in 2020 that they filled through 2017-2019. No pitcher in the table above faced more than 4.5 batters per game in 2020, a jump of less than 1 batter from the previous qualifier. So we see they all kept their role as relievers who pitched in short outings.
Here is a look at how all of the pitchers’ ERA in 2017-2019 (labelled pERA) compares to their ERA (labelled ERA) after the rule change. The line y=x on the graph represents no change between the periods, and if a pitcher is above the line their ERA was larger in 2020 and thus worse. The opposite is true if they are below the line.
We can see that there are a few pitchers whose 2020 ERA was significantly higher than their ERA in the previous period. Overall, 6 of the pitchers’ ERA was better than the previous period, and 7 pitchers posted a higher ERA. One interesting thing to take away from the graph is that Ryan Buchter–who posted the lowest ERA in the period 2017-2019–saw his ERA jump by nearly 2 runs. Ten games isn’t a big enough sample size to draw a certain conclusion, but perhaps some part of his game could have been affected by the changed role. The 2020 season wasn’t kind to Sam Coonrod, as he saw his ERA inflate to a large total in 18 games, while the other two pitchers with over-8 ERAs had fewer games played. There also doesn’t appear to be a relationship between pitchers with low ERA prior to this past season and their ERA in 2020, so perhaps this means that these pitchers’ performance overall (measured by ERA at least) could depend on a case-by-case basis, rather than the overly simplistic explanation of pitchers who had success before the rule change continued to see those results and below-average pitchers had their weaknesses exploited.
Looking at other stats, here is how their ERA, WHIP, hits per 9 innings, walks per 9 innings and strikeouts per 9 innings compare across the two periods. Graphs of each stat–ERA has already been covered–will be investigated after the table, the table is sorted by 2020 ERA. All stats are per fangraphs.com
The next figure compares how the pitchers stats fared from the periods of 2017-2019 to 2020.
In terms of pitchers allowing baserunners to reach, we see a much bigger difference in the number of pitchers on the sides of the line compared to ERA. Nine pitchers are above the line y=x and just 4 are below the line, indicating that the majority of the pitchers being compared saw their WHIP jump after the rule change. This is an interesting point, as the roles of these pitchers had been short outings, now that they are staying in the game longer, the number of batters they face that they allow to reach per inning has gotten worse as they face more.
Considering that only 7 saw their ERA rise–compared to the 9 who saw their WHIP rise–maybe while batters are more likely to reach base they are at least being prevented from scoring. What unfortunately is unknown from these scenarios is whether these innings were started by the relievers or not. If a pitcher is called into a game when the previous pitcher left runners on base, inheriting runners, it will be advantageous for the pitching team to call on a pitcher who minimizes batters reaching base, which would advance the runners. So while it’s likely that a trend is emerging considering that the majority of pitchers have regressed in both stats, more analysis can be done into other stats.
Once again, the majority of pitchers saw their hits allowed per nine innings rise. There are three pitchers that are very close to the line, three that improved their H/9 noticeably and seven whose ability to limit hits was worse in 2020. This is roughly in line with what we would expect as the previous stats analyzed showed similar results, especially considering the fact that walks and hits allowed went up as a sum. It is interesting though that both of the two pitchers who had the highest hits allowed per nine from 2017-2019 (the two points furthest right) both improved their H/9 in 2020, though Phillip Diehl only appeared in 10 games from 2017-2019 and 6 in 2020, so his performance is unfair to judge from the small sample size. Aaron Loup however, had a much larger sample size, so his improvement to the second best H/9 from the second worst in the sample is a notable observation from this graph.
Whereas H/9 showed a similar trend to WHIP, we see something different in analyzing the walks per nine innings. The number of players who improved in 2020 is just 5, and two pitchers are right on the line. Since only six pitchers saw a large jump in BB/9 this indicates that the pitchers as a whole perhaps did not get more selective with their pitch selection as their role expanded, even if it expanded to facing hitters who had the platoon advantage against them. There were three pitchers however who not only raised their BB/9 in 2020, but saw huge spikes. These pitchers were Taylor Guilbeau, Ryan Buchter and Brian Moran. Moran’s season as a whole left more to be desired by the majority of his stats, though only appearing in 7 games is not a huge sample. Guilbeau was very impressive in 2020, though it was only in 8 games, so posting a BB/9 of 7.04 with a 1.17 ERA seems to defy expectation of what happens when you surrender that many free passes. Perhaps the rule change did have an effect on the pitches that Buchter threw, as he walked more than 5 batters (up to 9.00 from 3.84) per nine innings this past season, in a slightly larger 10 game sample size.
We see something interesting when examining the pitchers’ strikeouts per nine innings. We see three players sit almost right on the line y=x, Luis Avilan had a 9.71 SO/9 from 2017-2019 and a 9.72 SO/9 in 2020, Adam Kolarek had a 6.27 SO/9 in 2017-2019 followed by a 6.16 SO/9 and Jose Alvarez raised his SO/9 slightly in 2020 from 8.17 to 8.53. For these three players the rule change had seemingly no effect on their ability to record punchouts. The cases of Taylor Guilbeau and Brian Moran are opposites, but interesting; Guilbeau recorded the worst SO/9 in the sample in both periods. Moran may not have had the greatest season by most measures but showed that he has an impressive ability to strike batters out, as he posted the highest number in the sample among both years. Though both of those players posted lower strikeout rates in 2020 the fact that they kept their respective ranks as the lowest and highest after the rule change is interesting.
Other than the plot for ERA, this plot appears to be the most evenly distributed in terms of the number of pitchers on either side of the line. It appears that for the pitchers in the middle of the range who saw a drop in their SO/9, saw their rate drop by more on average than the rate of the pitchers who saw a rise in theirs, albeit not by much. Considering that there isn’t a large trend in the players as a group seeing their strikeout rates either rise or fall, this visual lends itself to the fact that the rule change may have a pitcher-specific effect on strikeout rate.
When the MLB announced the rule change, it wasn’t clear what was going to happen to relievers who made a career of facing one or two batters and then leaving the game. Post rule change, those pitchers would have to adapt to the changing game. As a group, it appears those specialists, who appeared in the 2017-2019 and 2020 seasons didn’t uniformly see a decrease in performance as their roles expanded. Certain stats appeared to have taken a drop in performance among the specialist pitchers more than others after the rule changed. Though it is clear that should the rule be kept into the 2021 season and beyond, it could be an underlying reason why some pitchers may not be able to survive these changes, while others likely depend on the pitchers in question.
Jack Hinde
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